This invention relates to a spindle orientation control apparatus employing a magnetic sensor and, more particularly, to a spindle orientation control system having a simplified magnetic sensor contruction, and which enables the spindle to be stopped at a predetermined orientation with a high degree of accuracy.
Machine tools with an automatic tool change function well known in the art. These are machine tools perform machining work automatically while various tools are changed, automatically. In order to smoothly mate a desired tool with the machine tool spindle, it is necessary to stop a specified portion of the spindle at a predetermined commanded angular position with a high degree of accuracy. The same is true for boringtype machine tools when inserting a boring rod into a hole previously drilled in a workpiece. Thus the need to accurately stop a specified portion of a spindle at a predetermined angular position or orientation is quite common in mechanical machining operations.
It is conventional practice to stop a spindle at a predetermined orientation by using a mechanical control mechanism or pin mechanism. However, the pin, which serves as the stopping member, can be damaged by an externally applied force or by a machine malfunction, and the control mechanism is subject to wear due to the effects of friction. Such phenomena make it impossible to stop the spindle at the predetermined orientation, thereby impeding the smooth changing of tools or the insertion of boring rods. Avoiding the above usually entails troublesome maintenance and inspection work as well as the frequent replacement of parts.
The present invention therefore seeks to provide a spindle orientation control system which is capable of accurately stopping a specified portion of a spindle at a predetermined angular position through purely electrical means, which allows the use of a contactless magnetic sensor as position deviation signal generating means, and which simplifies the construction of the magnetic sensor.